slapos_accounting: get payment mode from the trade condition's payment condition

master/bt5/slapos_accounting/SkinTemplateItem/portal_skins/slapos_simulation/SaleInvoiceTransaction_postSlapOSGeneration.py

@@ -11,6 +11,16 @@ price_currency = invoice.getPriceCurrency()
 if invoice.getResource() != price_currency:
   invoice.setResource(price_currency)
 
+trade_condition = invoice.getSpecialiseValue(
+  portal_type=(
+    'Purchase Trade Condition',
+    'Sale Trade Condition',
+    'Internal Trade Condition',
+  )
+)
+if (invoice.getPaymentMode("") == "") and (trade_condition is not None):
+  invoice.setPaymentModeValue(trade_condition.getPaymentConditionPaymentMode())
+
 if invoice.getCausality(None) is None:
   causality_list = []
   for line in invoice.objectValues():